To meet the need of the multi-medium computer system nowadays, the integrated circuit memory device has been recently used for storing huge amount of information such as voice and image information. The information such as voice or image has characteristics of continuity of data. In other words, those information are, most of the time, stored and retrieved sequentially or serially.
In the conventional arts, there are two approaches to handle the issue of the digital voice storage. The first approach uses one single chip integrating the voice controller function as well as the voice storage memory function therein. This kind of system approach has a drawback of system inflexibility. For instance, the minimum capacity requirement of the integrated circuit memory device for 12 inches voice recording system differs from that for 6 inches. Under this situation, though the controller within the single chip still meet the users' need, the whole single chip should be replaced just because the limitation of the memory function itself.
The second approach is a two-chip solution, as disclosed in FIG. 1. The first single chip 13 takes care of the voice controller function and the second single chip 11 takes care of the voice storage issue. This approach obviously has a better system flexibility than the first one. However, many drawbacks are inherent with this approach. The first drawback relates to too many pins being required. Taking 256K SRAM as an example, the interface pins required at least include A0-A14 address lines, D0-D7 data lines, memory read (RD) and memory write (WR) lines, chip select (CS) control line, Vdd and Vss lines. The second drawback relates to the feasibility of the expansion of the memory size. When the requirement of expanding from 256K to 1M bits evolves, new address line A15, A16 are needed for the second single chip 11. The third drawback relates to the pin requirement on the first single chip 13. Since the controller 11 has to know if the memory chip 11 is exhausted for a memory operation, a plurality of selection signal, M1, M2 indicative of the memory type used are required for the controller 13. In FIG. 1, device 15 is an indication light, the device 17 is a speaker and the device 19 is a microphone.
To overcome the shortcomings as recited above inherent with the conventional arts, the first object of the invention is to provide a serial access memory device which has less pins requirement than that of the conventional arts.
The second object of the invention is to provide a serial access memory device which requires only a data line, an address clock line, a clock line as well as an access control signal to access the serial access memory device.
The third object of the invention is to provide a serial access memory device the pin configuration of which is independent of its memory size.
The fourth object of the invention is to provide a serial access memory device in which a plurality of memory locations may be accessed by receiving a first address value of the memory operation from the controller.